Emulsion of polymer having (meth)acrylate unit and adhesive compositions containing the emulsion

ABSTRACT

An emulsion of a polymer, in which the polymer comprises (a) a recurring unit derived from a (meth)acrylate and (b) a recurring unit derived from a vinyl compound having a group of --SO 3  R in which R is a hydrogen atom, an alkali metal atom or ammonium ion. The emulsion forms a film on an adherend to decrease the infiltration into the adherend, exhibits an adhesion force to a hydroxyapatite structure, a cement, a metal or a mineral when it is applied thereto to form a film by only drying around room temperature without washing it with water, and exhibits excellent affinity to a radical-polymerizable acrylic resin composition.

This is a continuation-in-part application based on U.S. patentapplication Ser. No. 08/066,211 filed on May 25, 1993, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to an emulsion of a polymer having a(meth)acrylate unit and adhesive compositions containing the emulsion.More specifically, it relates to a polymer emulsion which reacts to befixed on the surface of a solid containing a polyvalent cation reactivewith a sulfonic acid group, such as a hydroxyapatite structure, cement,a metal compound or a mineral, an adhesive film from the polymeremulsion formed on the surface of said solid and an adhesive compositionwhich exhibits excellent adhesion to a substrate.

The above adhesive film exhibits excellent adhesion to a tooth andexcellent sealability to dental tubules, so that it can be suitably usedas a dental primer and a dental anti-hypersensitivity film.

For treating a hydroxyapatite structure such as a dentin for remedy, anadhesive material such as 4-META/MMA-TBB (Superbond, supplied by SunMedical Co., Ltd) has been hitherto used. The adhesive material isbonded by a method in which a drilling dust is removed by preliminaryetching of an adherend surface with an acid, the adhesive material isapplied and cured and then a radical-polymerizable acrylic resin isfilled and cured. Since, however, the acid used for the above acidtreatment is a low molecular weight compound, it may infiltrate deepinto the hydroxyapatite structure. Therefore, when a dentin is treatedfor remedy, the acid comes to remove a healthy part of the dentin aswell and sometimes reaches a dental pulp to attack the nerve and give anacute pain.

Therefore, when a portion near to a dental pulp is treated for remedy,there has been conventionally employed a method in which the attack inbonding is prevented by applying onto the above portion a carboxylatecement which is a combination of a polymer type polyaerylle acid withzinc oxide or a glass ionomer cement which is a combination of ahomopolymer of polyacrylic acid or a copolymer from acrylic acid andeither itaconic acid or maleic acid with aluminosilicate glass.

Since, however, these cements are very poor in adhesion, there have beenproblems such as secondary caries and coming off of the attachment forremedy.

For the therapeutical treatment of the hypersensitivity of a dentinbased on exposure of dental tubules in the mouth, there are used aliniment of silver nitrate, potassium oxalate or disodiumhydrogenphosphate/calcium chloride (Ikemura, Imal, Journal of JapaneseDentistry Preservation Society, vol. 35, 26 (1992)), a toothpastecontaining citric acid or sodium citrate, a glass ionomer cement and a4-META-containing adhesive resin (D liner, supplied by Sun Medical Co.,Ltd).

The above preparations against the hypersensitivity of a dentin have thefollowing advantages. The liniment is free of stimulation to a dentalpulp and coloring, and the toothpaste obviates the therapeuticaltreatment in a dentist's chair. However, it is usual that it takes along period of time before they exhibit their effects. The polymer typecarboxylic acid such as glass ionomer hardly affects a dentin. However,it is poor in adhesion to a dentin and resistance to water, and itseffect does not continue satisfactorily. On the other hand, the adhesiveresin shows its effect, but is used for the therapy by a method in whicha portion to be treated is preliminarily etched with a low molecularweight acid such as a 10% citric acid-3% ferric chloride aqueoussolution or the like, and a solution prepared by mixing a curing agentand a monomer immediately before use is applied and polymerized.Therefore, it still involves a problem in the influence of the lowmolecular weight compound on a dentin and handling.

Further, VARNAL® (CETYLITE INDUSTRIES INC. (U.S.A.)) is commerciallyavailable, which is used for alleviating the cervical hyperesthesis byapplying it in the form of a solution to the dental surface of cervicalhyperesthesis and drying it to form a film. This method of treating atooth surface is similar to that employed in the present invention.However, VARNAL is a solution prepared by dissolving a copal resin whichis a natural resin in an alcohol solvent, and is basically differentfrom the present invention in the following points: VARNAL does notcontain any sulfonic acid group which is an essential component for theemulsion of an emulsion-polymerizable polymer of the invention, it maynot be facile to acquire the copal resin since it is a natural resin anddifficult to synthesize, and VARNAL is poor in adhesion to a tooth.

For decreasing the infiltration of an acid into a hydroxyapatitestructure and imparting it with affinity to an acrylic resin, thepresent Applicant has proposed an acrylate copolymer containing asulfonic acid group which allows to ion-bond or chelate-bond to acalcium component of the hydroxyapatite structure (Japanese Laid-openPatent Publications Nos. 171,024/1985 and 261,442/1990).

The polymer disclosed in the above Japanese Laid-open PatentPublications is specifically an acrylic copolymer produced frommethacrylate such as methyl methacrylate and a sulfonic acidgroup-containing monomer such as p-styrenesulfonic acid and/ormethacrylate macromet having a vinyl group at its terminal such asmethyl polymethacrylate. These Publications disclose a method in whichthe above acrylic copolymer is dissolved in a solvent such as water orethanol, the resultant solution is applied directly to a hydroxyapatitestructure surface without acid etching and the resultant coating iswashed with water. In this method, the degree of infiltration into thehydroxyapatite structure is small, the copolymer firmly bonds to thehydroxyapatite structure since the sulfonic acid group bonds to acalcium component of the hydroxyapatite structure, and thehydroxyapatite structure can be bonded to an acrylic resin to form alayer thereon since the polymethyl methacrylate portion of the acryliccopolymer and the acrylic resin have good affinity.

However, further studies of the above acrylic copolymer have revealedthe following. When a solution of the acrylic copolymer is applied anddried without washing it with water, the acrylic copolymer sometimesshows no adhesion force due to a presence of a remaining unreactedacrylic copolymer which does not react with the hydroxyapatitestructure. It is therefore essential to carry out a step of washing withwater for obtaining a stable adhesion force.

It is an object of the present invention to provide a novel adhesiveemulsion to overcome the above problems and an adhesive compositioncontaining the same.

It is another object of the present invention to provide a noveladhesive emulsion which decreases the infiltration into an adhererid,like a conventional sulfonic acid group-containing copolymer, whichexhibits an adhesion force to a hydroxyapatite structure, a cement, ametal or a mineral when it is applied thereto and, without washing itwith water, only dried around room temperature to form a film, whichexhibits excellent affinity to a radical-polymerizable acrylic resincomposition, and which further permits sealing the surface of ahypersensitive dentin since a film formed therefrom has the property ofbonding to a dentin which is a hydroxyapatite structure.

Other objects and advantages of the present invention will be apparentfrom the following description.

SUMMARY OF THE INVENTION

According to the present invention, the above objects and advantages ofthe present invention are achieved, first, by an emulsion of a polymer,in which the polymer comprises (a) a recurring unit derived from a(meth)acrylate and (b) a recurring unit derived from a vinyl compoundhaving a group of --SO₃ R in which R is a hydrogen atom, an alkali metalatom or ammonium ion and is derived from a mixture containing the(meth)acrylate and the vinyl compound having a group of --SO₃ R in whichR is as dellned above in a (meth)acrylate:vinyl compound molar ratio of99:1 to 50:50 by a soap-free emulsion polymerization.

The polymer emulsion according to the present invention may be anemulsion of a polymer which further contains (c) a recurring unitderived from a vinyl compound containing a group of --COOR₄ in which R₄is a hydrogen atom, an alkali metal atom or ammonium ion, or a group of--OPO(OR₅)₂ in which R₅ is a hydrogen atom, an alkali metal atom orammonium ion and is derived from a mixture containing the(meth)acrylate, the vinyl compound having a group of --SO₃ R in which Ris as defined above, and the vinyl compound containing a group of--COOR₄ or a group of --OPO(OR₅)₂ in which R₄ and R₅ are as definedabove in the molar ratio of (meth)acrylate:total of the two vinylcompounds of 99:1 to 50:50 and in the molar ratio of the vinyl compoundhaving a group of --SO₃ R in which R is as defined above to the vinylcompound containing a group of --COOR₄ or a group of --OPO(OR₅)₂ inwhich R₄ and R₅ are as defined above of 99:1 to 1:99.

The above (a) recurring unit derived from (meth)acrylate has the formula(A) for example, ##STR1## wherein R₁ is a hydrogen atom or an alkylgroup having 1 to 5 carbon atoms and R₂ is an alkyl group having 1 to5-carbon atoms.

The above (b) recurring unit derived from a vinyl compound having agroup of --SO₃ R has the formula (B), ##STR2##

wherein R₃ is a hydrogen atom or an alkyl group having 1 to 5 carbonatoms and R is a hydrogen atom, an alkali metal atom or ammonium ion.

Further, according to the present invention, there is provided a polymeremulsion obtained by emulsion-polymerizing (meth)acrylate in thepresence of the above emulsion polymer as an emulsifying agent.

Still further, according to the present invention, there is provided thefollowing polymer emulsions: (1) a polymer emulsion obtained byemulsion-polymerizing (meth)acrylate in the presence of an emulsion of apolymer as an emulsifying agent, said polymer of the latter emulsion astile emulsifying agent being obtained by emulsion-polmerizing (a) a(meth)acrylate and (b1) a vinyl compound having a group of --SO₃ R inwhich R is a hydrogen atom in the absence of a soap in an (a):(b1) molarratio of 99:1 to 50:50.

(2) a polymer emulsion obtained by emulsion-polymerizing (meth)acrylatein the presence of an emulsion of a polymer as an emulsifying agent,said polymer of the latter emulsion as the emulsifying agent beingobtained by emulsion-polymerizing (a) a (meth)acrylate and (b1) a vinylcompound having a group of --SO₃ R in which R is an alkali metal atom orammonium ion in the absence of a soap in an (a):(b1) molar ratio of 99:1to 50:50, and thereafter converting said group of --SO₃ R to --SO₃ Hgroup.

(3) a polymer emulsion obtained by emulsion-polymerizing (meth)acrylatein the presence of an emulsion of a polymer as an emulsifying agent,said polymer of the latter emulsion as the emulsifying agent beingobtained by emulsion-polymerizing (a) a (meth)acrylate, (b1) a vinylcompound having a group of --SO₃ R in which R is a hydrogen atom and(c1) a vinyl compound containing a group of --COOR₄ in which R₄ is ahydrogen atom, or a group of --OPO(OR₅)₂ in which R₅ is a hydrogen atom,in the absence of a soap in the molar ratio of (meth)acrylate (a):totalof the two vinyl compounds (b1) and (c1) of 99:1 to 50:50 and in themolar ratio of the vinyl compound (b1):the vinyl compound (cl) of 99:1to 1:99.

(4) a polymer emulsion obtained by emulsion-polymerizing (meth)acrylatein the presence of an emulsion of a polymer as an emulsifying agent,said polymer of the latter emulsion as the emulsifying agent beingobtained by emulsion-polymerizing (a) a (meth)acrylate, (b1) a vinylcompound having a group of --SO₃ R in which R is an alkali metal atom orammonium ion and (c1) a vinyl compound containing a group of --COOR₄ inwhich R₄ is an alkali metal atom or ammonium ion, or a group of--OPO(OR₅)₂ in which R₅ is an alkali metal atom or ammonium ion, in theabsence of a soap in the molar ratio of (meth)acrylate (a):total of thetwo vinyl compounds (b1) and (c1) of 99:1 to 50:50 and in the molarratio of the vinyl compound (b1):the vinyl compound (c1) of 99:1 to1:99, and thereafter converting said groups of --SO₃ R, --COOR₄ and--OPO(OR₅)₂ to --SO₃ H, --COOH and --OPO(OH)₂, respectively.

The recurring unit derived from the (meth)acrylate preferably has theabove formula (A) and the recurring unit derived from the vinyl compoundhaving a group of --SO₃ H has the above formula (B) wherein R is ahydrogen atom.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polymer emulsion according to the present invention is produced, forexample, by emulsion-polymerizing a (meth)acrylate of the formula (A1),##STR3##

wherein R₁ and R₂ are as defined in the above formula (A),

with a sulfonic acid group-containing monomer of the formula (B1),##STR4##

wherein R₃ and R are as defined in the above formula (B),

preferably in an (A1): (B1) molar ratio of 99: 1 to 50:50 or byhomopolymerizing one (meth)acrylate monomer of the formula (A1), orcopolymerizing (meth)acrylate monomers of the formula (A1), in thepresence of the so-obtained emulsion polymer as an emulsifying agent.

Further, in the production of the polymer emulsion according to thepresent invention, the polymer emulsion is produced byemulsion-polymerizing the vinyl compounds of the above formulae (A1) and(B1) and either (E) a vinyl compound having a group of --COOR₄ or (F) avinyl compound having a group of --OPO(OR₅)₂ in which R₄ and R₅ are asdefined above, preferably in an (A1):(B1)+(E) or (A1):(B1)+(F) molarratio of 99:1 to 50:50 and in a (B1):(E) or (B1):(F) molar ratio of 99:1to 1:99, or by homopolymerizing one (meth)acrylate monomer of theformula (A1), or copolymerizing (meth)acrylate monomers of the formula(A1), in the presence of the so-obtained emulsion polymer as anemulsifying agent.

Being constituted by the specific recurring units, the emulsion polymerobtained in the present invention can form a film having the excellentproperty of bonding to a sulfonic acid group of a hydroxyapatitestructure, a cement, a metal compound or a mineral. Therefore, a dentinsuch as a hypersensitive dentin surface can be sealed with an adhesivefilm. Further, since it shows excellent affinity to aradical-polymerizable acrylic resin, it can be properly used as anadhesive for bonding a dentin and a radical-polymerizable acrylic resin.

The adhesive emulsion, process for the production thereof and adhesivecomposition containing the same, provided by the present invention, willbe explained hereinafter.

First, the process for the production of the adhesive emulsion will beexplained. In the present invention, the term "emulsion polymer" refersto a polymer obtained by emulsion polymerization, and the term "polymeremulsion" refers to an emulsion of the emulsion polymer.

The polymer emulsion (to be referred to as "EM" hereinafter) in thepresent invention can be produced by subjecting a (meth)acrylate of theabove formula (A1) and a vinyl compound having a group of --SO₃ R inwhich R is a hydrogen atom, an alkali metal atom or ammonium ion,represented by the above formula (B1), to a known emulsionpolymerization method (e.g., "Polymer Latex", Soichi Murol, Ikuo Morino,published as Shin-Kobunshi Bunko).

In the formula (A1), R₁ is a hydrogen atom or an alkyl group having 1 to5 carbon atoms. Specific examples of the alkyl group include methyl,ethyl, propyl, butyl and pentyl. R₁ is preferably an alkyl group having1 to 5 carbon atoms, more preferably methyl.

Further, R₂ is an alkyl group having 1 to 5 carbon atoms. Specificexamples of the alkyl group include methyl, ethyl, propyl, butyl andpentyl. R₂ is preferably methyl, ethyl or butyl, more preferably methyl.

Examples of the compound of the above formula (A1) preferably include(meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate,butyl (meth)acrylate, propyl (meth)acrylate, pentyl (meth)acrylate,glycidyl (meth)acrylate, 2-hydroxy (meth)acrylate and 3-hydroxy(meth)acrylate.

Of the above (meth)acrylates, preferred are methyl methacrylate, ethylmethacrylate and butyl methacrylate, and particularly preferred ismethyl methacrylate.

In the present invention, there is used another monomer having a groupof --SO₃ R in which R is a hydrogen atom, an alkali metal atom orammonium ion. Specifically, the monomer includes vinyl compounds oralkyl group-substituted vinyl compounds to which the group of --SO₃ R inwhich R is as defined above bonds directly or through other group.

Examples of the above sulfonic acid group-containing monomer preferablyinclude allylsulfonic acid, methallylsulfonic acid, vinylsulfonic acid,o-styrenesulfonic acid, m-styrenesulfonic acid, p-styrenesulfonic acid,tert-butylacrylamidesulfonic acid, alkali metals salts of these acidssuch as lithium salts, potassium salts and sodium salts, and ammoniumsalts of the above acids. Of these, preferred are compounds in which theabove group of --SO₃ R bonds to a carbon atom which is part of apolymerizable group, such as styrenesulfonic acids. These compounds arepreferably represented by the above formula (B1).

In the above formula (B1), R₃ is a hydrogen atom or an alkyl grouphaving 1 to 5 carbon atoms. The alkyl group includes methyl, ethyl,propyl, butyl and pentyl. R₃ is preferably a hydrogen atom.

The position at which the group of --SO₃ R bonds may be any one of theo-position, m-position and p-position in the benzene ring. In view ofthe adhesion to an adherend, preferred is the p-position. Further, thegroup of --SO₃ R may be any one of a lithium salt, potassium salt,sodium salt and ammonium salt. Examples of the compound of the aboveformula (B1) preferably include sulfonic acid compounds such asallylsulfonic acid, methallylsulfonic acid, vinylsulfonic acid,sulfoethyl methacrylate, tert-butylacrylamidesulfonic acid andp-styrenesulfonic acid, and sodium salts and ammonium salts of these. Ofthese examples, preferred is p-styrenesulfonic acid.

Examples of the above (E) monomer having a group of --COOR₄ in which R₄is a hydrogen atom, an alkali metal atom or ammonium ion includeunsaturated monovalent carboxylic acids such as acrylic acid,methacrylic acid, vinylacetic acid, crotonic acid,methacryloyloxybenzoic acid, vinylsalicylic acid andvinylacetylsalicyclic acid; alkali metal salts of these acids; ammoniumsalt compounds of these acids; unsaturated polyvalent carboxylic acidssuch as maleic acid, fumaric acid, itaconic acid, aconitic acid,citraconic acid, mesaconic acid and 4-methacryloyloxyethyltrimelliticacid; alkali metal salts of these acids; and ammonium acid compounds ofthese acids. Of these, preferred are acrylic acid and methacrylic acid.

Examples of the above (F) monomer having a group of --OPO(OR₅)₂ in whichR₅ is a hydrogen atom, an alkali metal atom or ammonium ion includephosphate ester monomers such as acid phosphoethyl (meth)acrylate,3-chloro-2-acid phosphopropyl (meth)acrylate, acid phosphooxypropyl(meth)acrylate, acid phosphooxypolyoxyethylethylene glycolmono(meth)acrylate and acid phosphooxypolyoxypropylene glycolmono(meth)acrylate; alkali metal salts of these; ammoniumsalt-containing monomers of these; and those compounds derived from theabove compounds in which the hydroxyl group is substituted with othersubstituent, i.e., phosphate ester type monomers such as2-(meth)acryloyloxyethylphenyl phosphate and 2-(meth)acryloyloxyethyl4-methoxyphenyl phosphate. Of these, acid phosphooxyethyl methacrylateor acid phosphooxyethylene glycol monomethacrylate is useful.

In the emulsion polymerization in the present invention, the molar ratioof the monomor of the above formula (A1) to the monomer of the aboveformula (B1) is preferably as shown below, since an excellent emulsioncan be obtained and since the acidity decreases to prevent theinfiltration into an adherend. That is, the molar ratio of the monomerof the formula (A1) and the monomer of the formula (B1) is preferably99:1 to 50:50, more preferably 95:5 to 60:40. Further, concerning themolar ratio of the monomer of the formula (A1) and the monomer of theformula (B1) and either the (E) vinyl compound having a group of --COOR₄or the (F) vinyl compound having a group of --OPO(OR₅)₂ in which R₄ andR₅ are as dellned above, preferably, the (A1):(B1)+(E) or (B1)+(F) molarratio is 99:1 to 50:50 and that the (B1):(E) or (F) molar ratio is 99:1to 1:99, and more preferably, the (A1):(B1)+(E) or (B1)+(F) molar ratiois 95:5 to 60:40 and that the (B1):(E) or (F) molar ratio is 99:1 to5:95.

The reaction conditions for the emulsion polymerization are notspecially limited. For example, an excellent polymer emulsion can beproduced, for example, by adding a mixture of (A1) and (B1) or (A1),(B1) and optionally either (E) or (F) to water in an amount of 60 partsby weight or less per 100 parts by weight of the water at a temperatureranging from room temperature to 100° C., addling an initiator foremulsion polymerization and polymerizing them for tens minutes to 24hours. When the monomer mixture is added at one time, an emulsioncontaining a large amount of aggregates is liable to be formed. It istherefore preferred to add the monomer mixture Intermittently.

The emulsion polymerization may be carried out in the presence orabsence of a surfactant such as an anionic surfactant, a cationicsurfactant, a nonionic surfactant or a polymer surfactant such aspolyethylene glycol. In the absence of a surfactant, however, there canbe produced a polymer emulsion which is free of aggregates, has highstability in water and has an emulsion particle diameter of 1 μm orless. For simple post-treatment and for avoiding the impairment of theadhesion and film strength of the polymer emulsion, it is preferred tocarry out soap-free emulsion polymerization in the absence of asurfactant. Further, when the above monomer (E) or (F) is used, it ispreferred to produce the emulsion under an acidic condition of pH 6 orless for maintaining the emulsion stability in a good state.

In addition to the above monomers, other monomer which is generallyemulsion-polymerizable may be copolymerized in such an amount that doesnot impair the properties of the adhesive composition of the presentinvention. Examples of the "other monomer" include glycidyl esters suchas N-(2-hydroxy-3-methacryloyloxypropyl)-N-phenylglycine, glycidyl(meth)acrylate and N-acrylglycine; (meth)acrylates having an alkylaminogroup such as N,N-dimethylaminoethyl (meth)acrylate, aminoethyl(meth)acrylate and hydroxyethylaminoethyl (meth)acrylate; olefins suchas ethylene, propylene and 1-butene; vinyl halides such as vinylchloride, vinylidene chloride, vinyl bromide, 2-chloroethyl(meth)acrylate, 1,1-dichloroethylene and tetrachloroethylene; vinylesters such as vinyl acetate and vinyl propionate; (meth)acrylaldehydessuch as (meth)acrylaldehyde and 3-cyano(meth)acrylaldehyde; vinyl etherssuch as methyl vinyl ether, isobutyl vinyl ether, (meth)acrylaldehydediacetate, (meth)acrylaldehyde diethyl acetal and 1,2-dimethoxyethylene;alkenylbenzenes such as styrene, vinyltoluene, α-methylstyrene,chloromethylstyrene, stilbene and 1,1-diphenylethylene; vinyl cyanidecompounds such as acrylonitrile and methacrylonitrile; (meth)acrylamidessuch as (meth)acrylamide, N-vinylphthalamide, N-vinylsuccinamide,N,N-dimethylacrylamide, N-hydroxymethyl(meth)acrylamide andN-hydroxyethyl-2-methylacrylamide; and (meth)acrylates having a hydroxylgroup such as hydroxylmethyl (meth)acrylate, 2-hydroxyethyl(meth)acrylate and 4-hydroxybutyl (meth)acrylate.

The process for the production of an emulsion polymer byhomopolymerizing or copolymerizing (meth)acrylate(s) (A1) in thepresence of the above-obtained polymer emulsion (EM) as an emulsifyingagent will be explained hereinafter.

The (meth)acrylate(s) used in the above process are the compound(s) ofthe formula (A1).

In this process, specific examples of the alkyl group as R₁ and R₂ inthe formula (A1) also include methyl, ethyl, propyl, butyl and pentyl.R₁ is preferably an alkyl group, more preferably methyl. R₂ ispreferably methyl.

In this process, preferred examples of the compound of the formula (A1)include alkyl esters of (meth)acrylic acids such as methyl(meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, propyl(meth)acrylate, pentyl (meth)acrylate and glycidyl (meth)acrylate.

Of the above (meth)acrylates, methyl methacrylate is particularlypreferred.

The method of emulsion-polymerization of the (meth)acrylate of theformula (A1) has a characteristic feature in that the above-detailedpolymer emulsion "EM" is used as an emulsifying agent.

The above polymer emulsion "EM" may be added to the (meth)acrylatecompound of the formula (A1) as an emulsifying agent after it has beentaken out of a reaction vessel. Further, the above polymer emulsion "EM"may be used in a manner in which the (meth)acrylate compound of theformula (A1) is added to it while it is in a reaction vessel, i.e.,without being taken out of a reaction vessel, after it has beenproduced.

The reaction conditions are not specially limited, while, for example,the polymer emulsion can be produced by adding the (meth)acrylatecompound of the formula (A1) to the polymer emulsion "EM" within thetemperature range between room temperature and 100° C. after the polymeremulsion has been produced, and emulsion-polymerizing the resultantmixture for tens minutes to 24 hours.

The mixing ratio of the polymer emulsion "EM" and the monomer of theformula (A1) and the amounts of these based on water are not speciallylimited. Preferably, the "EM": (A1) weight ratio is 1:99 to 80:20, andthe total amount of "EM" and the monomer (A1) per 100 parts by weight ofwater is 60 parts by weight or less.

The type of the emulsion polymer and the composition of the copolymercan be varied by intermittently changing the kind of the (meth)acrylatecompound (A1) and the composition of the mixture in the polymerizationsystem.

For forming an adhesive film having higher adhesion strength by applyingthe polymer emulsion of the present invention to a hydroxyapatitestructure, preferably, a tooth and the surface of cervicalhyperesthesia, all of --SO₃ R, --CO₂ R₄ and --OPO(OR₅)₂ as componentsforming the emulsion are substantially acid types,.1.e., --SP₃ H, --CP₂H and --OPO(OH)₂. That is because the adhesion strength increases as theproportion of acid types in acid groups increases.

For the above purpose, it is preferred to employ a method in which,after the production of "EM", the above R, R₄ and R₅ (each of R, R₄ andR₅ is an alkali metal atom or ammonium ion) are replaced with hydrogenatoms using mineral acids such as hydrochloric acid and sulfuric acid oran ion-exchange resin and then (A1) is emulsion-polymerized or a methodin which (A1) is emulsion-polymerized in the presence of "EM" as anemulsifier and then --SO₃ R, --CO₂ R₄ and --OPO(OR₅)₂ (each of R, R₄ andR₅ is an alkali metal atom or ammonium ion) are converted to acid typesby the above method.

Further, after the emulsion polymer is converted to an acid type, it ispreferred to remove compounds having low molecular weights such assodium chloride and sodium sulfate by a dialysis method or anultrafiltration method, if they are formed.

In the above polymer emulsion, other monomer may be compolymerized inaddition to the compound of the formula (A1) in such an amount that doesnot impair the adhesion ability and film strength of the polymeremulsion of the present invention. The above "other monomer" includesgenerally emulsion-polymerizable monomers. That is, the "other monomer"is selected from olefins such as ethylene, propylene and butene-1; vinylhalides such as vinyl chloride, vinylidene chloride and vinyl bromide;vinyl esters such as vinyl acetate and vinyl propinonate; vinyl etherssuch as methyl vinyl ether, ethyl vinyl ether and isobutyl vinyl ether;alkenylbenzenes such as styrene, vinyltoluene, α-methylstyrene,chloromethylstyrene and stilbene; and vinyl cyanide compounds such asacrylonitrile and methacrylonitrile.

The so-produced polymer emulsion of the present invention exhibitsexcellent stability in water for a long period of time and can be alsoformed into a film which exhibits excellent adhesion to an adherendstructure having a polyvalent cation reactive to a sulfonic acid group,since the emulsion polymer has a sulfonic acid unit.

Further, the polymer emulsion of the present invention is insoluble inwater, so that a film formed therefrom is excellent in water resistance.Meanwhile, a film formed from a conventional water-soluble polymerhaving a sulfonic acid group or from an emulsion obtained by emulsionpolymerizing a monomer in the presence of the conventional water-solublepolymer as an emulsifier is poor in water resistance, and it is notpractical to use such a film under wet conditions in the mouth.

When the polymer emulsion is used as a film for the above-describedpurpose, the adhesion strength tends to decrease as the SO₃ H group as acomponent forming the emulsion is neutralized. Therefore, preferably atleast 50 mol %, more preferably at least 90 mol%, particularlypreferably 100 mol %, of the --SO₃ R group (R is a hydrogen atom, analkali metal atom or an ammonium ion) is --SO₃ H.

When the polymer emulsion of the present invention is used as anadhesive or a surface treating agent, it is preferred to use it in astate in which it is dispersed in a polar solvent such as water and analcohol, e.g. as ethanol. In particular, when it is used for a dentalpurpose, it is preferred to use it in a dispersion in water or awater-ethanol mixed solvent. The solid content of the polymer emulsionin the above dispersing medium is generally 0.05 to 20% by weight,preferably 0.5 to 15% by weight.

For improving the reactivity of the above polymer emulsion with anadherend, a low molecular weight acid may be optionally added in such anamount that does not impair the stability of the emulsion and the waterresistance of the film, i.e., in an amount of several to thousands interms of ppm unit. The low molecular weight acid includes citric acid,oxalic acid, maleic acid, phosphoric acid and EDTA.

The above polymer emulsion may contain known additives as required, suchas a coloring pigment, a loading pigment, an aggregate, a wetting agentand a thickener.

A film can be formed simply by applying the polymer emulsion of thepresent invention to an adherend having a polyvalent cation reactivewith a sulfonic acid group, allowing it to stand for a few seconds to afew minutes and drying it with compressed air or the like at roomtemperature. It is assumed that the sulfonic acid group of each emulsionparticle being oriented in the solvent direction chemically bonds to anadherend during the above process, whereby each emulsion particle bondsto the adherend.

Further, the dried film is completely removed from an adherendunreactive with a sulfonic acid group such as glass by washing it withwater, while it is maintained on an adherend reactive with a sulfonicacid group such as hydroxyapatite even when it is washed with water.Therefore, formation of a film firmly bonded to a dentin can beattained, and it is suitable as a dentin protection film such as asealing film against the hypersensitivity of a dentin. Further, thisfilm can serve to bond an adherend to an acrylic resin, since itcontains a poly(meth)acrylate component having high affinity to theacrylic resin.

The polymer emulsion of the present invention can be used in thefollowing agents due to 1rs properties and by employing an industriallyusable treatment method: an anti-fogging agent, a drop removing agent, afiller for an ion adsorption column, an antistatic agent, an epoxycuring agent, a photoresist sealing agent, a sludge coagulating agent, ahardening agent for cements such as alumina cement, magnesium cement andPortland cement and gypsum, a reinforcement, a hardening agent for glassionomer cement, zinc phosphate cement and a hydroxyapatite powder, anadhesive for bonding a structure which is reactive with the presentemulsion to wood, an adhesive for wood used in house construction and amusical instrument, and a treating agent for coating paper.

The polymer emulsion of the present invention is, as described above, anemulsion of a copolymer containing recurring units of a sulfonic acidgroup and a (meth)acrylate, or an emulsion of a copolymer containingrecurring units of a sulfonic acid group, a (meth)acrylate and either acarboxyl group or a phosphate ester group. Therefore, it can be formedinto a film which exhibits adhesion to an adherend containing apolyvalent cation reactive with a sulfonic acid group. Further, it alsoexhibits excellent affinity to a radical-polymerizable acrylic resin.Since the formed film is firmly bonded to an adherend surface which canreact with a sulfonic acid group, it is not removed by washing it withwater. This film is useful as a dentin protection film, particularlyuseful against the hypersensitivity of a dentin. As will be described inExample 44 later, this film has been found to have an effect on at least90% of volunteer patients, thus giving an excellent clinical result.When an attempt has been made to bond a hydroxyapatite structure to amaterial for remedy by using the polymer emulsion of the presentinvention, it has shown a maximum adhesion strength of 8,2 MPa, whilecommercially available materials (Comparative Examples 5 to 8) andlinear (meth)acrylate/p-styrenesulfonic acid copolymers (without theprocedures of washing with water) (Comparative Examples 9 and 10) haveshown an adhesion strength of about 0 to 0.3 MPa. With the polymeremulsion of the present invention, the therapeutical treatment of thehypersensitivity of a dentin and the operation of a hydroxyapatitestructure for remedy can be performed with simple procedures and withmore reliability.

The present invention will be explained hereinafter more in detail byreference to Examples, which, however, shall not be limitative to thepresent invention.

In Examples, methyl methacrylate and acrylic acid were distilled underreduced pressure, and then dissolved oxygen was removed by degassingunder nitrogen bubbling Just before use. Acid phosphooxyethylmethacrylate (Phosmer M, supplied by Unichemical Co., Ltd.) and sodiump-styrenesulfonate (Spinomer, purity 85%, supplied by Tosoh Corp.) wereused as they were commercially available.

EXAMPLE 1 (E-1)

Distilled water (25 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,1.0 g of methyl methacrylate (hereinafter referred to as "MMA"), 0.27 gof sodium p-styrenesulfonate (hereinafter referred to as "SSNa",Spinomer, supplied by Tosoh Corp.), and 30 mg of potassium persulfateand 10 mg of sodium hydrogen sulfite as polymerization initiators wereadded, and the mixture was vigorously stirred at 60° C. for 2 hours. 4.0Grams of MMA, 1.1 g of SSNa, 70 mg of potassium persulfate and 20 mg ofsodium phosphite were further added, and the mixture was vigorouslystirred for 22 hours and then cooled to room temperature to give anemulsion having a solid content of 5.8 wt. %. Concentrated hydrochloricacid (0.47 ml) was added, and the mixture was stirred for 2 hours andthen placed in a dialysis tube. The mixture was dialyzed in distilledwater for 5 days while the distilled water was changed to new one eachday. The dialysis tube was dried at room temperature under atmosphericpressure to give an emulsion having a solid content of 8.5 wt. %.

The infrared spectrum (IR) of the above-obtained emulsion polymer showedthat it contained MMA and styrenesulfonic acid units. When the polymerwas also analyzed with GPC using, as a reference, polymethylmethacrylate whose molecular weight was known, it had a number averagemolecular weight (Mn) of 1.0×10⁶. Further, the elemental analysis of thepolymer-showed that the MMA unit content was 91.0 mol %.

EXAMPLE 2 (E-2)

Distilled water (32 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,1.0 g of MMA, 0.16 g of SSNa, 30 mg of potassium persulfate and 10 mg ofsodium hydrogen sulfite were added, and the mixture was vigorouslystirred at 60° C. for 2 hours. Then, 1 g of MMA, 0.16 g of SSNa, 10 mgof potassium persulfate and 3 mg of sodium hydrogen sulfite wereintermittently added six times at intervals of 30 minutes with the samecomponents and amounts as described above each time, and the mixture wasvigorously stirred for 19 hours. The reaction mixture was cooled to roomtemperature, and after 0.38 ml of concentrated hydrochloric acid wasadded, the mixture was fully stirred for 2 hours. The mixture was placedin a dialysis tube and dialyzed in distilled water for 5 days while thedistilled water was changed to new one each day. The dialysis tube wasdried at room temperature under atmospheric pressure to give an emulsionhaving a solid content of 10.7 wt. %.

The IR of the above emulsion polymer showed that it contained MMA andstyrenesulfonic acid units. The polymer was analyzed in the same manneras in Example 1 to show Mn of 7.5×10⁵. Further, the elemental analysisof the polymer showed that the MMA unit content was 94.1 mol %.

EXAMPLE 3 (E-3)

Distilled water (35 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,1.0 g of MMA, 0.12 g of SSNa, 30 mg of potassium persulfate and 10 mg ofsodium hydrogen sulfite were added, and the mixture was vigorouslystirred at 60° C. for 2 hours. Then, 2.0 g of MMA, 0.24 g of SSNa, 30 mgof potassium persulfate and 10 mg of sodium hydrogen sulfite were added,and the mixture was vigorously stirred for 30 minutes. Then, 4.0 g ofMMA, 0.48 g of SSNa, 60 mg of potassium persulfate and 20 mg of sodiumhydrogen sulfite were added, and the mixture was vigorously stirred for21.5 hours. The reaction mixture was cooled to room temperature, andafter 0.29 ml of concentrated hydrochloric acid was added, the mixturewas stirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 5 days while the distilled water waschanged to new one each day. The dialysis tube was dried at roomtemperature under atmospheric pressure to give an emulsion having asolid content of 11.2 wt. %.

The IR of the above emulsion polymer showed that it contained MMA andstyrenesulfonic acid units. The polymer was analyzed in the same manneras in Example 1 to show Mn of 6.2×10⁵. Further, the elemental analysisof the polymer showed that the MMA unit content was 95.7 mol %.

EXAMPLE 4 (E-4)

Distilled water (41 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,1.0 g of MMA, 0.08 g of SSNa, 30 mg of potassium persulfate and 10 mg ofsodium hydrogen sulfite were added, and the mixture was vigorouslystirred at 60° C. for 2 hours. Further, 2.0 g of MMA, 0.16 g of SSNa, 23mg of potassium persulfate and 3 mg of sodium hydrogen sulfite wereadded three times at intervals of 30 minutes, and further, the mixturewas vigorously stirred for 21.5 hours. The reaction mixture was cooledto room temperature, and after 0.19 ml of concentrated hydrochloric acidwas added, the mixture was stirred for 2 hours. The mixture was placedin a dialysis tube and dialyzed in distilled water for 5 days while thedistilled water was changed to new one each day. The dialysis tube wasdried at room temperature under atmospheric pressure to give an emulsionhaving a solid content of 16.9 wt. %.

The IR of the above emulsion polymer showed that it contained MMA andstyrenesulfonic acid units. The polymer was analyzed in the same manneras in Example 1 to show Mn of 5.9×10⁵. Further, the elemental analysisof the polymer showed that the MMA unit content was 96.7 mol %.

EXAMPLE 5 (E-5)

Distilled water (55 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,1.0 g of MMA, 0.06 g of SSNa, 30 mg of potassium persulfate and 10 mg ofsodium hydrogen sulfite were added, and the mixture was vigorouslystirred at 60° C. for 2 hours. Further, 2.0 g of MMA, 0.12 g of SSNa, 23mg of potassium persulfate and 3 mg of sodium hydrogen sulfite wereadded three times at intervals of 30 minutes, and further, the mixturewas vigorously stirred for 21.5 hours. The resultant emulsion had asolid content of 8.8 wt. %. The emulsion was cooled to room temperature,and after 0.14 ml of concentrated hydrochloric acid was added, themixture was stirred for 2 hours. The mixture was placed in a dialysistube and dialyzed in distilled water for 5 days while the distilledwater was changed to new one each day. The dialysis tube was dried atroom temperature under atmospheric pressure to give an emulsion having asolid content of 14.7 wt. %.

The IR of the above emulsion polymer showed that it contained MMA andstyrenesulfonic acid units. The polymer was analyzed in the same manneras in Example 1 to show Mn of 1.6×10⁶. Further, the elemental analysisof the polymer showed that the MMA unit content was 97.6 mol %.

EXAMPLE 6 (E-6)

Distilled water (50 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,2.0 g of MMA, 1.2 g of SSNa, 30 mg of potassium persulfate and 10 mg ofsodium hydrogen sulfite were added, and the mixture was vigorouslystirred at 60° C. for 2.5 hours. Further, 1.0 g of MMA, 15 mg ofpotassium persulfate and 7 mg of sodium hydrogen sulfite were added fourtimes at intervals of 30 minutes, and further, the mixture wasvigorously stirred for 19.5 hours. The reaction mixture was cooled toroom temperature, and after 0.4 ml of concentrated hydrochloric acid wasadded, the mixture was stirred for 2 hours. The mixture was placed in adialysis tube and dialyzed in distilled water for 5 days while thedistilled water was changed to new one each day. The dialysis tube wasdried at room temperature under atmospheric pressure to give an emulsionhaving a solid content of 9.1 wt. %.

The elemental analysis of the polymer showed that the MMA unit contentwas 92.6 mol %.

EXAMPLE 7 (E-7)

Distilled water (50 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,2.0 g of MMA, 0.54 g of SSNa, 30 mg of potassium persulfate and 10 mg ofsodium hydrogen sulfite were added, and the mixture was vigorouslystirred at 60° C. for 2.5 hours. Further, 1.0 g of MMA, 15 mg ofpotassium persulfate and 7 mg of sodium hydrogen sulfite were added fourtimes at intervals of 30 minutes, and further, the mixture wasvigorously stirred for 19.5 hours. The reaction mixture was cooled toroom temperature, and after 0.19 ml of concentrated hydrochloric acidwas added, the mixture was stirred for 2 hours. The mixture was placedin a dialysis tube and dialyzed in distilled water for 5 days while thedistilled water was changed to new one each day. The dialysis tube wasdried at room temperature under atmospheric pressure to give an emulsionhaving a solid content of 10.9 wt. %.

The elemental analysis of the polymer showed that the MMA unit contentwas 96.9 mol %. This polymer emulsion was observed through atransmission microscope to show that it contains particles having adiameter of 0.1 to 0.5 μm.

EXAMPLE 8 (E-8)

Distilled water (50 ml) was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,2.0 g of MMA, 0.48 g of SSNa, 30 mg of potassium persulfate and 10 mg ofsodium hydrogen sulfite were added, and the mixture was vigorouslystirred at 60° C. for 2 hours. Further, 1.0 g of MMA, 15 mg of potassiumpersulfate and 7 mg of sodium hydrogen sulfite were added four times atintervals of 30 minutes, and further, the mixture was vigorously stirredfor 20 hours. The reaction mixture was cooled to room temperature, andafter 0.17 ml of concentrated hydrochloric acid was added, the mixturewas stirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 5 days while the distilled water waschanged to new one each day. The dialysis tube was dried at roomtemperature under atmospheric pressure to give an emulsion having asolid content of 10.5 wt. %.

The elemental analysis of the polymer showed that the MMA unit contentwas 98.5 mol %.

EXAMPLE 9 (EA-1)

While 60 ml of a hydrochloric acid aqueous solution having pH of 2 wastemperature-increased to 60° C., an argon gas was bubbled therein for 20minutes. Under argon atmosphere, 2.00 g (20 mmol) of MMA, 0.24 g (3.3mmol) of acrylic acid (hereinafter referred to as "AA"), 0.61 g (2.5mmol) of SSNa, 30 mg of potassium persulfate (hereinafter referred to as"KPS") and 10 mg of sodium hydrogen sulfite (hereinafter referred to as"NHS") were added, and the mixture was vigorously stirred at 60° C. for2.5 hours. 15 Minutes after the monomers had been added, the mixturebecame a bluish white solution.

Further, 1.00 g (10 mmol) of MMA, 30 mg of KPS and 15 mg of NHS wereadded, and then 1 g of MMA was added three times at intervals of 20minutes. After 30 mg of KPS and 15 mg of NHS had been added, the mixturewas stirred until the total reaction time was as long as 24 hours. Thereaction mixture was cooled to room temperature, and after 0.21 ml ofconcentrated hydrochloric acid was added, the mixture was furtherstirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day to give an emulsion having a solid contentof 5.7wt. %.

The IR of the above emulsion polymer showed that it contained MMA, AAand styrenesulfonic acid (hereinafter referred to as "SSA") units.Further, the elemental analysis (hereinafter referred to as "EA") of thepolymer showed that the SSA and AA unit contents were 7.2 and 13.1 mol%,respectively.

EXAMPLE 10 (EA-2)

While 70 ml of a hydrochloric acid aqueous solution having pH of 2 wastemperature-increased to 60° C., an argon gas was bubbled therein for 20minutes. Under argon atmosphere, 2.00 g (20 mmol) of MMA, 0.24 g (3.3mmol) of AA, 0.29 g (1.2 mmol) of SSNa, 30 mg of KPS and 10 mg of NHSwere added, and the mixture was vigorously stirred for 2.5 hours. 15Minutes after the monomers had been added, the mixture became a bluishwhite solution.

Further, 1.00 g (10 mmol) of MMA, 30 mg of KPS and 15 mg of NHS wereadded, and then 1 g of MMA was added three times at intervals of 20minutes. After 30 mg of KPS and 15 mg of NHS had been added, the mixturewas stirred until the total reaction time was as long as 24 hours. Thereaction mixture was cooled to room temperature, and after 0.10 ml ofconcentrated hydrochloric acid was added, the mixture was furtherstirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day to give an emulsion having a solid contentof 8.1 wt. %.

The IR of the above emulsion polymer showed that it contained MMA, SSAand AA units. Further, the EA of the polymer showed that the SSA and AAunit contents were 3.2 and 27.8 mol %, respectively.

EXAMPLE 11 (EA-3)

While 70 ml of a hydrochloric acid aqueous solution having pH of 2 wastemperature-increased to 60° C., an argon gas was bubbled therein for 20minutes. Under argon atmosphere, 2.00 g (20 mmol) of MMA, 0.24 g (3.3mmol) of AA, 0.17 g (0.7 mmol) of SSNa, 30 mg of KPS and 10 mg of NHSwere added, and the mixture was vigorously stirred for 2.5 hours. 15Minutes after the monomers had been added, the mixture became a bluishwhite solution.

Further, 1.00 g (10 mmol) of MMA, 30 mg of KPS and 15 mg of NHS wereadded, and then 1 g of MMA was added three times at intervals of 20minutes. After 30 mg of KPS and 15 mg of NHS had been added, the mixturewas stirred until the total reaction time was as long as 24 hours. Thereaction mixture was cooled to room temperature, and after 0.06 ml ofconcentrated hydrochloric acid was added, the mixture was furtherstirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day to give an emulsion having a solid contentof 5.6wt. %.

The IR of the above emulsion polymer showed that it contained MMA, SSAand AA units.

EXAMPLE 12 (EP-1)

While 70 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled therein for 20 minutes. Under argon atmosphere,2.00 g (20 mmol) of MMA, 0.71 g (3.4 mmol) of Phosmer M, 0.63 g (2.6mmol) of SSNa, 30 mg of KPS and 10 mg of NHS were added, and the mixturewas vigorously stirred for 3 hours. 20 Minutes after the monomers hadbeen added, the mixture became a bluish white solution.

Further, 1.00 g (10 mmol) of MMA, 30 mg of KPS and 15 mg of NHS wereadded, and then 1 g of MMA was added three times at intervals of 20minutes. After 30 mg of KPS and 15 mg of NHS had been added, the mixturewas stirred until the total reaction time was as long as 24 hours. Thereaction mixture was cooled to room temperature, and after 0.22 ml ofconcentrated hydrochloric acid was added, the mixture was furtherstirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day to give an emulsion having a solid contentof 7.1 wt. %.

The IR of the above emulsion polymer and the analysis thereof with anX-ray light electron analyzing apparatus (supplied by ShimadzuCorporation, hereinafter referred to as "ESCA") showed that it containedMMA, SSA and Phosmer M. Further, the EA of the polymer showed that theSSA and Phosmer M unit contents were 8.0 and 16.1 mol %, respectively.

EXAMPLE 13 (EP-2)

While 70 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled therein for 20 minutes. Under argon atmosphere,2.00 g (20 mmol) of MMA, 0.74 g (3.5 mmol) of Phosmer M, 0.30 g (1.2mmol) of SSNa, 30 mg of KPS and 10 mg of NHS were added, and the mixturewas vigorously stirred for 3 hours. 10 Minutes after the monomers hadbeen added, the mixture became a bluish white solution.

Further, 1 g (10 mmol) of MMA, 30 mg of KPS and 10 mg of NHS were added,and then 1 g of MMA was added three times at intervals of 20 minutes.After 30 mg of KPS and 10 mg of NHS had been added, the mixture wasstirred until the total reaction time was as long as 24 hours. Thereaction mixture was cooled to room temperature, and after 0.10 ml ofconcentrated hydrochloric acid was added, the mixture was furtherstirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day to give an emulsion having a solid contentof 6.2 wt. %.

The IR and ESCA of the above emulsion polymer showed that it containedMMA, SSA and Phosmer M. Further, the EA of the polymer showed that theSSA and Phosmer M unit contents were 5.3 and 2.7 mol %, respectively.

EXAMPLE 14 (EP-3)

While 70 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled therein for 20 minutes. Under argon atmosphere,2.00 g (20 mmol) of MMA, 0.65 g (3.1 mmol) of Phosmer M, 0.17 g (0.7mmol) of SSNa, 30 mg of KPS and 10 mg of NHS were added, and the mixturewas vigorously stirred for 3 hours. 5 Minutes after the monomers hadbeen added, the mixture turned bluish white.

Further, 1 g (10 mmol) of MMA, 30 mg of KPS and 10 mg of NHS were added,and then 1 g of MMA was added three times at intervals of 20 minutes.After 30 mg of KPS and 10 mg of NHS had been added, the mixture wasstirred until the total reaction time was as long as 24 hours. Thereaction mixture was cooled to room temperature, and after 0.06 ml ofconcentrated hydrochloric acid was added, the mixture was furtherstirred for 2 hours. The mixture was placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day to give an emulsion having a solid contentof 6.5 wt. %.

The IR and ESCA of the above emulsion polymer showed that it containedMMA, SSA and Phosmer M. Further, the EA of the polymer showed that theSSA and Phosmer M unit contents were 2.5 and 7.7 mol %, respectively.

COMPARATIVE EXAMPLE 1

All the monomers used in Example 1 were added at one time. That is, 25ml of distilled water was temperature-increased to 60° C., and anitrogen gas was bubbled therein for 1 hour. Under nitrogen atmosphere,5.0 g of MMA, 1.37 g of SSNa, 100 mg of potassium persulfate and 30 mgof sodium hydrogen sulfite were added at once. In this case, a largeamount of aggregates were formed, and no emulsion was obtained.

COMPARATIVE EXAMPLE 2

The emulsion polymerization was carried out in the same manner as inExample 9 except that AA was replaced with sodium acrylate (hereinafterreferred to as "ANa"). That is, while 60 ml of distilled water wastemperature-increased to 60° C., an argon gas was bubbled therein for 20minutes. Under argon atmosphere, 2.00 g (20 mmol) of MMA, 0.28 g (3mmol) of ANa, 0.61 g (2.5 mmol) of SSNa, 30 mg of KPS and 10 mg of NHSwere added, and the mixture was vigorously stirred at 60° C.. After 20minutes., a large amount of aggregates were formed, and no emulsion wasobtained.

COMPARATIVE EXAMPLE 3

The same emulsion polymerization as that of Example 9 was carried out indistilled water. That is, while 60 ml of distilled water wastemperature-increased to 60° C., an argon gas was bubbled therein for 20minutes. Under argon atmosphere; 2.00 g (20 mmol) of MMA, 0.24 g (3mmol) of AA, 0.61 g (2.5 mmol) of SSNa, 30 mg of KPS and 10 mg of NHSwere added, and the mixture was vigorously stirred at 60° C.. Since theformation of a large amount of aggregates was observed after 15 minutes,the reaction was discontinued.

COMPARATIVE EXAMPLE 4 (EMMA)

While 50 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled therein for 20 minutes. Then, 250 mg of sodiumlaurylsulfate was added, and the mixture was fully stirred. Thereafter,10 g (0.1 mol) of MMA, 100 mg of KPS and 10 mg of NHS were added, andthe monomers were polymerized for 5 hours. The resultant product wascooled to room temperature, placed in a dialysis tube and dialyzed indistilled water for 7 days while the distilled water was changed to newone each day to give an emulsion having a solid content of 15.7 wt. %.

EXAMPLES 15-24

Fresh emulsion bovine teeth were polished in water with awater-resistant emery paper (#600) to expose enamels or dentins.Adhesion surfaces were defined by masking tapes having a hole whosediameter was 5.4 mm. Each of the polymer emulsions (E-1 to E-8) obtainedin Examples 1 to 8 was adjusted to a solid content of 5 wt. %, and thenapplied to the adhesion surface in an amount of 3 μl. The appliedemulsions were allowed to stand for 1 minutes, and lightly blown bycompressed air to form films. MMA was softly applied to the resultantadhesion surfaces twice with a dental brush. Then, acryl rods having adiameter of 6 mm were planted thereon with an MMA-tri-n-butylborane(TBB) resin (X) whose TBB was a polymerization catalyst, and allowed tostand at room temperature for 1 hour to cure the resin. The teeth withthe acryl rods planted thereon were immersed in water at 37° C. for 24hours and measured for adhesion strength by subjecting them to a tensiletest using an autograph. (supplied by Shimadzu Corporation) with a crosshead speed of 2 mm/min.

The above procedures after the film formation were repeated using aspontaneous polymerization resin (Y) containing BPO-p-toluldine as acatalyst (Methafast, supplied by Sun Medical Co., Ltd), to measureadhesion strength in the same manner as above.

Further, films were formed in the same manner as above, and a bondingagent (Z) containing 0.5 wt. % of d,l-camphorquinone, 0.5 wt. % ofdiethylaminobenzoic acid and 99.0 wt. % of triethylene glycoldimethacrylate was applied in an amount of 10 μl and exposed to lightfrom a visible light irradiator (Translux, supplied by Kulzer) for 20seconds. Then, acryl rings having an internal diameter of 6 mm and aheight of 1 mm were placed thereon, and Photobright US (supplied byKuraray Co., Ltd.) was filled within the ring-formed circles and furtherexposed to light for 1 minute. Acryl rods were planted with Methafast,and measured for adhesion strength in the same manner as above. Table 1shows the results.

                  TABLE 1                                                         ______________________________________                                               Emulsion                                                                      (concentration       Bovine teeth                                                                            Adhesion                                       of 5 wt. %)  Dental  Enamel (EN)/                                                                            strength                                Example                                                                              Code         resin*  Dentin (DE)                                                                             (MPa)                                   ______________________________________                                        15     E-1          X       EN        3.1                                     16     E-2          X       EN        1.1                                     17     E-3          X       EN        1.8                                     18     E-5          X       EN        2.3                                     19     E-7          X       EN        8.2                                     20     E-7          X       DE        2.6                                     21     E-7          Y       EN        2.5                                     22     E-7          Z       EN        4.0                                     23     E-7          Z       DE        1.0                                     24     E-6          X       EN        2.3                                     Blank  No adhesive film                                                                           X       EN        1.0                                            No adhesive film                                                                           X       DE        0                                              No adhesive film                                                                           X       EN        0                                              No adhesive film                                                                           Y       DE        0                                              No adhesive film                                                                           Y       EN        0.7                                     ______________________________________                                         *Notes)                                                                       X: MMATBB resin                                                               Y: MMABPO-DMPT resin                                                          X: 3GCQ-DEABA resin                                                      

EXAMPLES 25-30

Emulsions obtained in Examples (EA-1 to EA-3 and EP-1 to EP-3) wereadjusted to a solid content of 5 wt. %, and measured for adhesionstrength to enamel in the presence of an MMA/TBB resin (X) in the samemanner as above. Table 2 shows the results.

                  TABLE 2                                                         ______________________________________                                               Emulsion                                                                      (concentration      Bovine teeth                                                                            Adhesion                                        of 5 wt. %) Dental  Enamel (EN)/                                                                            strength                                 Example                                                                              Code        resin*  Dentin (DE)                                                                             (MPa)                                    ______________________________________                                        25     EA-1        X       EN        3.0                                      26     EA-2        X       EN        2.4                                      27     EA-3        X       EN        2.4                                      28     EP-1        X       EN        3.4                                      29     EP-2        X       EN        2.5                                      30     EP-3        X       EN        3.4                                      ______________________________________                                         *Note:                                                                        X: MMATBB resin                                                          

COMPARATIVE EXAMPLES 5-8

Fresh emulsion bovine teeth were polished in water with water-resistantemery paper up to #600. The tooth surface areas were defined by maskingtapes having a hole whose diameter was 5.4 mm. Further, acryl ringshaving an internal diameter of 6 mm and a height of 1 mm were placedthereon, and a commercially available polymer cement was applied withinthe ring-formed circles and cured. Then, an MMA-TBB resin was filledtherein, and the polymer cement was measured for adhesion strength inthe same manner as above. The polymer cement was prepared from HybondGlass Ionomer (HYG, supplied by Shofusha) or Ketac cement (KC, suppliedby ESPE) in accordance with the methods specified by each supplier.Table 3 shows the results.

COMPARATIVE EXAMPLES 9-10

The tensile test was carried out by using an MMA/p-styrenesulfonic acidcopolymer disclosed in Japanese Laid-Open Patent PublicationNo.171,024/1985, i.e., a linear MMA-p-styrenesulfonic acid polymerobtained by reacting MMA with SSNa in a water/ethanol-containing solventand post-treating the resultant reaction product. That is, the copolymerhaving an MMA content of 70 mol % (MS-7) and the copolymer having an MMAcontent of 90 mol % (MS-9) were prepared and measured for adhesionstrength using a MMA-TBB resin (X) in the same manner as above. Table 3shows the results.

                  TABLE 3                                                         ______________________________________                                                Polymer                                                                       cement             Bovine teeth                                                                            Adhesion                                 Comp.   and      Dental    Enamel (EN)/                                                                            strength                                 Example MS       resin*    Dentin (DE)                                                                             (MPa)                                    ______________________________________                                        5       HYG      X         EN        0.1                                      6       KC       X         EN        0.3                                      7       HYG      X         DE        0                                        8       KC       X         DE        0.2                                      9       MS-7     X         DE        0                                        10      MS-9     X         DE        0.3                                      ______________________________________                                         *Note:                                                                        X: MMATBB resin                                                          

EXAMPLE 31

The latex (E-7) having a concentration of 0.05 wt. % was applied to anenamel and dentin, allowed to stand for 1 minute and dried with air. Theresultant film was washed with water for 30 minutes, dried and observedthrough a scanning electron microscope (JMS-5400, JEOL) at anacceleration voltage of 30 KV to show that the film remained on thesurfaces, i.e., that the film did not come off when washed with water,since it bonded to the adherends. An adhesion strength to the enamel was2.0 MPa when MMA-TBB was used as a bonding agent.

COMPARATIVE EXAMPLE 11

A glass surface used as an adhesion surface under the same conditions asthose in Example 31 was observed to show no residual film, i.e., thatthe film completely came off when washed with water.

EXAMPLES 32-37

The surfaces of synthetic hydroxyapatite having a diameter of 3 mm(supplied by Pentax, hereinafter referred to as "HAP") were fullycleaned. The emulsions obtained in Examples (EA-1-EA-3 and EP-1-EP-3)were respectively adjusted to a solid content of 5 wt. %, and applied toHAP surfaces in an amount of 1 μl. The applied emulsions were allowed tostand for 1 minute, and lightly blown by compressed air to form films.The films were washed with water for 1 minute and dried. Each film wasevaluated for a residual ratio by examining C/Ca before the latices wereapplied and C/Ca after the films were washed with water by means of anX-ray light electron analyzing apparatus ESCA 500 supplied by ShimadzuCorporation, and calculated a ratio (C₁) of C/Ca's.

Table 4 shows the results.

COMPARATIVE EXAMPLE 12

Example 32 was repeated except that the emulsion was replaced with EMMAobtained in Comparative Example 4 and C/Ca ratio of the resultant filmwas calculated. Table 4 shows the results.

                  TABLE 4                                                         ______________________________________                                                       Emulsion                                                                      (concentration                                                                of 5 wt. %)                                                    Example        Code        C.sub.1 *                                          ______________________________________                                        32             EA-1        7.6                                                33             EA-2        4.7                                                34             EA-3        5.0                                                35             EP-1        4.0                                                36             EP-2        4.2                                                37             EP-3        5.4                                                Comparative    EMMA        0.8                                                Example 12                                                                    ______________________________________                                         *Note                                                                         ##STR5##                                                                 

EXAMPLES 38-43

While water was poured, fresh emulsion bovine teeth were polished withwater-resistant emery paper (#600) to expose enamels. The emulsionsobtained in Examples (EA-1 to EA-3 and EP-1 to EP-3) were adjusted to asolid content of 5 wt. %, and applied to adhesion surfaces in the amountof 1 μl. The applied emulsions were allowed to stand for 1 minute and,lightly blown with compressed air to form films. The films were washedwith water for 1 minute, dried and observed through a scanning electronmicroscope (JMS-5400, JEOL) at an acceleration voltage of 10 KV to showthat all the films remained and that no film came off.

EXAMPLE 44

The E-7 emulsion was adjusted to a solid content of 5 wt. %, and appliedto sixteen hypersensitive volunteer patients after approval by them.That is, their diseased parts were cleaned, and the emulsion was appliedthereto with tampons, allowed to stand and dried with air. Fifteenpatents out of the sixteen had a good effect and had no relapse for atleast 6 months.

EXAMPLE 45

(1) Calcium chloride was added to E-7 emulsion having a solid content of5 wt. % such that the amount of the calcium ehlorlde based on thesulfonic acid group of the E-7 emulsion was 3 equivalent weights. Themixture was shaken for 30 seconds and subjected to centrifugalseparation at 1,600 rpm for 10 minutes. The supernatant showed no MSemulsion, and all the contents coagulated.

(2) The above procedures (1) were repeated except that the 3 equivalentweight calcium chloride was replaced with a 1 equivalent weight aluminumchloride. The supernatant showed no MS emulsion, and all the contentscoagulated.

(3) E-7 emulsion having a solid content of 5 wt. % was subjected tocentrifugal separation at 1.600 rpm for 10 seconds to show nocoagulation.

EXAMPLE 46

The surfaces of synthetic hydroxyapatite pellets having a diameter of 10mm and a diameter of 4 mm were cleaned under water current withwater-resistant emery paper #600. At room temperature, E-6 emulsionhaving a solid content of 8 wt. % was applied to the synthetichydroxyapatite pellet having a diameter of 10 mm, and immediatelythereafter, the synthetic hydroxyapatite pellet having a diameter of 4mm was bonded thereto. The pellets were allowed to stand at roomtemperature for 12 hours as they were, and then a rod was planted on thesynthetic hydroxyapatite pellet having a diameter of 4 mm in thepresence of an instantaneous adhesive. Then, the pellets were subjectedto a tensile test with an autograph at a cross head speed of 2 mm/min.to show an adhesion strength of 24 kgf/cm². It is seen thathydroxyapatite pellets can be bonded to each other in the presence ofthe emulsion of the present invention.

For comparison, the above procedures were repeated except that the E-6emulsion was replaced with EMMA (Comparative Example 4). As a result,the adhesion strength was 0 kgf/cm², and it is seen that hydroxyapatitepellets cannot be bonded to each other in the presence of EMMA.

EXAMPLE 47 (E-9)

An emulsion containing 5% by weight of a polymer having --SO₃ H groupwas obtained in the same manner as in Example 1. This emulsion in anamount of 50 ml was vigorously stirred at 500 rpm while increasing thetemperature of the emulsion up to 80° C. under a nitrogen gas current.1.0 Gram of methyl methacrylate (MMA), 30 mg of potassium persulfate and10 mg of sodium hydrogen sulfite were added, and the mixture was stirredat 500 rpm for 30 minutes. Further, 1.0 g of MMA, 30 mg of potassiumpersulfate and 10 mg of sodium hydrogen sulfite were added, and themixture was further stirred for 20 hours. After the reaction, thereaction product was placed in a dialysis tube and dialyzed for 5 dayswhile changing distilled water each day. Then, the dialysis tube wasdried at room temperature under atmospheric pressure to give an emulsionhaving a solid content of 8.0 wt. %. During the polymerization and thedialyzing, the emulsion did not show any aggregation. The emulsion wasobserved by means of a scanning electron microscope (SEM) to show thatit had particles having a diameter of 0.1 to 0.5 μm.

EXAMPLE 48 (EA-4)

While 60 ml of a hydrochloric acid aqueous solution having a pH of 2 wastemperature-increased to 60° C., an argon gas was bubbled for 20minutes. Under argon gas atmosphere, 2 g of methyl methacrylate, 0.2 gof acrylic acid, 0.61 g of sodium p-styrenesulfonate, 30 mg of potassiumpersulfate and 10 mg of sodium hydrogen sulfite were added. The mixturebecame a bluish white solution 15 minutes after the addition of themonomers. After a total reaction time of 24 hours, the reaction mixturewas cooled to room temperature, and 0.21 ml of concentrated hydrochloricacid was added. The mixture was stirred for 2 hours, then placed in adialysis tube, and dialyzed in distilled water for 7 days while thedistilled water was changed to new one each day. After the dialysis, themixture was concentrated at room temperature to a solid content of 5% byweight to give an emulsion having an excellent dispersion state.

While 30 ml of the above emulsion was temperature-increased to 60° C.,an argon gas was bubbled for 20 minutes. Then, 0.5 g of methylmethacrylate, 15 mg of potassium persulfate and 8 mg of sodium hydrogensulfite were added, and after 20 minutes, 0.5 g of methyl methacrylate,15 mg of potassium persulfate and 8 mg of sodium hydrogen sulfite werefurther added. After a total reaction time of 24 hours, the reaction wasterminated to give an emulsion having a solid content of 7% by weight.The emulsion showed an excellent dispersion state, and no aggregationwas found.

EXAMPLE 49 (EP-4)

While 70 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled for 20 minutes. Under argon gas atmosphere, 2 g ofmethyl methacrylate, 0.71 g of Phosmer M, 0.63 g of sodiump-styrenesulfonate, 30 mg of potassium persulfate and 10 mg of sodiumhydrogen sulfite were added. The mixture became a bluish white solution15 minutes after the addition of the monomers. After a total reactiontime of 24 hours, the reaction mixture was cooled to room temperature,and 0.22 ml of concentrated hydrochloric acid was added. The mixture wasstirred for 2 hours, then placed in a dialysis tube and dialyzed indistilled water for 7 days while the distilled water was changed to newone each day. After the dialysis, the mixture was concentrated at roomtemperature to a solid content of 5% by weight to give an emulsionhaving an excellent dispersion state.

While 30 ml of the above emulsion was temperature-increased to 60° C.,an argon gas was bubbled for 20 minutes. Then, 0.5 g of methylmethacrylate, 15 mg of potassium persulfate and 8 mg of sodium hydrogensulfite were added. After 20 minutes, 0.5 g of methyl methacrylate, 15mg of potassium persulfate and 8 mg of sodium hydrogen sulfite wereadded. After a total reaction time of 24 hours, the reaction wasterminated to give an emulsion having a solid content of 7% by weight.The emulsion showed an excellent dispersion state, and no aggregationwas found.

COMPARATIVE EXAMPLE 13 (E-10)

While 410 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled for 20 minutes. Under argon gas atmosphere, 3 g(30 mmol) of MMA, 16.9 g (70 mol) of SSNa, 0.27 g of potassiumpersulfate (KPS) and 0.13 g of sodium hydrogen sulfite (NHS) were added,and the mixture was vigorously stirred for 2 hours. Then, 1 g (10 mmol)of MMA, 28 mg of KPS and 14 g of NHS were added, and after 20 minutes, 1g (10 mmol) of MMA, 28 mg of KPS and 14 mg g of NHS were further added,and after a total reaction time of 7 hours, the reaction mixture wascooled to room temperature. Then, 5.83 ml of concentrated hydrochloricacid was added, and the mixture was further stirred for 2 hours, thenplaced in a dialysis tube and dialyzed in distilled water for 7 dayswhile the distilled water was changed to new one each day. After thedialysis, the mixture was concentrated at room temperature to a solidcontent of 5% by weight. The polymer obtained in the presence ofMMA:SSNa (=30:70 mol %) as an emulsifier, and the polymer converted toan acid type, as above did not become opaque, and they were soluble inwater.

EXAMPLE 50 (E-11)

While 232 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled for 20 minutes. Under argon gas atmosphere, 3 g(30 mmol) of MMA, 7.2 g (30 mmol) of SSNa, 140 mg of potassiumpersulfate (KPS) and 47 mg of sodium hydrogen sulfite (NHS) were added,and the mixture was vigorously stirred. Then, 1 g (10 mmol) of MMA, 28mg of KPS and 14 mg of NHS were added, and after 20 minutes, 1 g (10mmol) of MMA, 28 mg of KPS and 14 mg of NHS were further added. After atotal reaction time of 7 hours, the reaction mixture was cooled to roomtemperature, and 2.5 ml of concentrated hydrochloric acid was added. Themixture was stirred for 2 hours, then placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day. After the dialysis, the mixture wasconcentrated at room temperature to a solid content of 5% by weight. Thepolymer obtained in the presence of MMA:SSNa (=50:50 mol %) as anemulsifier, and the polymer converted to an acid type, as above becameopaque, and they were emulsions of an emulsion polymer stably dispersedin water.

EXAMPLE 51 (E-12)

While 154 ml of distilled water was temperature-increased to 60° C., anargon gas was bubbled for 20 minutes. Under argon gas atmosphere, 3 g(30 mmol) of MMA, 3.1 g (12.8 mmol) of SSNa, 84 mg of potassiumpersulfate (KPS) and 28 mg of sodium hydrogen sulfite (NHS) were added,and the mixture was vigorously stirred. Then, 1 g (10 mmol) of MMA, 28mg of KPS and 14 mg of NHS were added, and after 20 minutes, 1 g (10mmol) of MMA, 28 mg of KPS and 14 mg of NHS were added. After a totalreaction time of 7 hours, the reaction mixture was cooled to roomtemperature, and 1.1 ml of concentrated hydrochloric acid was added. Themixture was stirred for 2 hours, then placed in a dialysis tube anddialyzed in distilled water for 7 days while the distilled water waschanged to new one each day. After the dialysis, the mixture wasconcentrated at room temperature to a solid content of 5% by weight. Thepolymer obtained in the presence of MMA:SSNa (=70:30 mol %) as anemulsifier, and the polymer converted to an acid type, as above becameopaque, and they were emulsions of an emulsion polymer stably dispersedin water.

EXAMPLE 52

Fresh emulsion bovine teeth were polished in water with awater-resistant emery paper (#600), and the so-polished enamels weredefined with masking tapes having a diameter of 5.4 mm. The emulsions ofthe emulsion polymers E-11 and E-12 and the water-soluble polymer E-10were respectively applied to the adhesion surfaces (defined surfaces) inan amount of 3 μl each. The applied emulsions were allowed to stand for1 minute, and slightly blown with compressed air to form films. Acrylrods having a diameter of 6 mm were planted on the film-formed surfaceswith an MMA-TBB resin, and allowed to stand for 1 hour. The bovine teethwith the acryl rods planted thereon were immersed in water at 37° C. for24 hours, and measured for adhesion strength by a tensile test at across head speed of 2 mm/minute. The films formed from E-10, E-11 andE-12 showed adhesion strengths of 1.0, 1.5 and 2.0 Mpa, respectively.The film formed from E-11 showed the lowest value of 1.0 MPA. Table 5shows the results.

COMPARATIVE EXAMPLE 14

Sodium hydrogencarbonate was added to each of E-10, E-11, E-12 and theemulsion of E-7 adjusted to a concentration of 5% so that they wererendered neutral or sulfonic acid groups were converted to sodiumsulfonates. The resultant emulsions are referred to as E-10/Na, E-11/Na,E-12/Na and E-7/Na. These emulsions were tested for adhesion in the samemanner as in Example 52. All the films formed from the above emulsionsshowed adhesion strengths of 0 MPa.

Table 5 shows the results.

EXAMPLE 53

Fresh emulsion bovine teeth were polished in water with awater-resistant emery paper (#600) to expose dentins, and the dentinswere polished with a tooth brush with a tooth paste (Apadent A, suppliedby Japan Apatite Limited) for 3 minutes. The bovine teeth were washedwith water, and ultrasonically treated in water for 30 minutes to cleanthe dental tubules of smear plugs. The resultant bovine teeth were usedas model surfaces for cervical hyperesthesia. E-7, EA-1, EP-1, E-10,E-11. E-12, E-7/Na, E-10/Na, E-11/Na and E-12/Na were adjusted to asolid content of 5% by weight, and applied to model surfaces with asponge. After 30 seconds, the model surfaces were slightly blown withcompressed air to form films. The film-formed surfaces were washed withwater for 1 minute. And, their SEM photographs (×2,000) were taken, andthe dental tubules sealing ratio was determined.

Dental tubules sealing ratio (%)=(number of dental tubules sealed withemulsion/total number of dental tubules)×100

The results were that E-7 (80%), (EA-1 (72 %), EP-1 (75%), E-10 (10%),E-11 (52%) and E-12 (65 %), and it was found that E-10 was inferior insealability since its dental tubules sealing ratio was and almost alldental tubules remained open. Further, E-7/Na, E-10/Na, E-11/Na andE-12/Na showed dental tubules sealing ratios of 0%.

Table 5 shows the results.

                  TABLE 5                                                         ______________________________________                                                    Tensile adhesion                                                                           Dental tubules                                       Emulsion No.                                                                              strength (MPa)                                                                             sealing ratio (%)                                    ______________________________________                                        E-7         8.2          80                                                   E-11        1.5          52                                                   E-12        2.0          62                                                   EA-1        3.0          72                                                   EP-1        3.4          75                                                   E-10        1.0          10                                                   E-7/Na      0             0                                                   E-10/Na     0             0                                                   E-11/Na     0             0                                                   E-12/Na     0             0                                                   ______________________________________                                    

EXAMPLE 54

The emulsion E-7 was adjusted to a solid content of 5% by weight, andsulfonic acid groups of this emulsion were neutralized by adding sodiumhydrogencarbonate to prepare an emulsion whose sulfonic acid groups wereconverted to sodium salts by 10 mol % (10Na), 50 mol % (50Na) or 100 mol% (100 Na). Then, the so-prepared emulsions were measured for adhesionstrength by the same tensile test as that in Example 52. The emulsionsshowed a tendency that the adhesion strength decreased with an increasein the molar ratio of sodium sulfonate to sulfonic acid group, and theresults were E-7 (8.2 MPa), 10Na (5.9 MPa), 50Na (3.0 MPa) and 100 Na (0MPa). Table 6 shows the results.

                  TABLE 6                                                         ______________________________________                                                                  Tensile                                                            SO.sub.3 H group                                                                         adhesion                                            Emulsion No.   (mol %)    strength                                            ______________________________________                                        E-7 (ONa)      100        8.2                                                 10 Na          90         5.9                                                 50 Na          50         3.0                                                 100 Na          0         0.0                                                 ______________________________________                                    

COMPARATIVE EXAMPLE 15

A commercially available preparation for preventing cervicalhyperesthesia (VARNAL, supplied by CETYLITE INDUSTRIES INC., U.S.A.) wastested for dental tubules sealability in the same manner as in Example53 to show that only 40% of the tubules were sealed.

What is claimed is:
 1. An emulsion of a water insoluble polymer, inwhich the polymer consists essentially of(a) a recurring unit derivedfrom a (meth)acrylate, (b) a recurring unit derived from a vinylcompound having a group of --SO₃ R in which R is a hydrogen atom, analkali metal atom or ammonium ion and (c) a recurring unit derived froma vinyl compound containing a group of --COOR₄ in which R₄ is a hydrogenatom, an alkali metal atom or ammonium ion, or a group of --OPO(OR₅)₂ inwhich R₅ is a hydrogen atom, an alkali metal atom or ammonium ion, andis derived from a mixture of the (a) (meth)acrylate, (b) the vinylcompound having the group of --SO₃ R and (c) the vinyl compoundcontaining the group of --COOR₄ or the group of --OPO(OR₅)₂ in the molarratio of (meth)acrylate:total of the two vinyl compounds of 99:1 to50:50 and in the molar ratio of the vinyl compound having the group of--SO₃ R to the vinyl compound containing the group of --COOR₄ or thegroup of --OPO(OR₅)₂ of 99:1 to 1:99 by a soap-free emulsionpolymerization, and wherein at least 50 mol % of the vinyl compoundhaving the group of --SO₃ R is a vinyl compound having the group --SO₃H.
 2. An emulsion of a water insoluble polymer obtained byemulsion-polymerizing (meth)acrylate in the presence of an emulsionconsisting essentially of the polymer recited in claim 1 as anemulsifying agent.
 3. An adhesive composition consisting essentially ofthe emulsion of the polymer recited in claim
 1. 4. An adhesivecomposition consisting essentially of the emulsion of the waterinsoluble polymer recited in claim
 2. 5. A dental adhesive compositionconsisting essentially of the emulsion of the water insoluble polymerrecited in claim
 1. 6. A dental adhesive composition consistingessentially of the emulsion of the water insoluble polymer recited inclaim
 2. 7. An adhesive composition consisting essentially of theemulsion of a water insoluble polymer consisting essentially of apolymer obtained by emulsion-polymerizing (meth)acrylate in the presenceof the emulsion of a water insoluable polymer as an emulsifying agent,said polymer of the latter emulsion as the emulsifying agent consistingessentially of a polymer obtained by emulsion-polymerizing (a) a (meth)acrylate and (b1) a vinyl compound having a group of --SO₃ R in which Ris hydrogen atom in the absence of a soap in an (a):(b1) molar ratio of99:1 to 50:50.
 8. An adhesive composition consisting essentially of theemulsion of a water insoluble polymer consisting essentially of apolymer obtained by emulsion-polymerizing (meth)acrylate in the presenceof the emulsion of a water insoluble polymer as an emulsifying agent,said polymer of the latter emulsion as the emulsifying agent consistingessentially of a polymer obtained by emulsion-polymerizing (a) a (meth)acrylate and (b1) a vinyl compound having a group of --SO₃ R in which Ris an alkali metal atom or ammonium ion in the absence of a soap in an(a):(b1) molar ratio of 99:1 to 50:50, and thereafter converting saidgroup of --SO₃ R to --SO₃ H group.
 9. An adhesive composition consistingessentially of emulsion of a water insoluble polymer consistingessentially of a polymer obtained by emulsion-polymerizing(meth)acrylate in the presence of a water insoluble polymer as anemulsifying agent, said polymer of the latter emulsion as theemulsifying agent consisting essentially of a polymer obtained byemulsion-polymerizing (a) a (meth) acrylate and (b1) a vinyl compoundhaving a group of --SO₃ R in which R is a hydrogen atom and (c1) a vinylcompound containing a group of --COOR₄ in which R₄ is a hydrogen atom ora group of --OPO(OR₅)₂ in which R₅ is a hydrogen atom, in the absence ofa soap in the molar ratio of (meth) acrylate (a): total of the two vinylcompounds (b1) and (c1) of 99:1 to 50:50 and the molar ratio of thevinyl compound (b1):the vinyl compound (c1) of 99:1 to 1:99.
 10. Anadhesive composition consisting essentially of the emulsion of a waterinsoluble polymer consisting essentially of a polymer obtained byemulsion-polymerizing (meth)acrylate in the presence of the emulsion ofa water insoluble polymer as an emulsifying agent, said polymer of thelatter emulsion as the emulsifying agent consisting essentially of apolymer obtained by emulsion-polymerizing (a) a (meth)acrylate, (b1) avinyl compound having a group of --SO₃ R in which R is an alkali metalatom or ammonium ion and (c1) a vinyl compound containing a group of--COOR₄ in which R4 is an alkali metal atom or ammonium ion, or a groupof --OPO(OR₅)₂ in which R₅ is an alkali metal atom or ammonium ion, inthe absence of a soap in the molar ratio of (meth)acrylate (a):total ofthe two vinyl compounds (b1) and (c1) of 99:1 to 50:50 and in the molarratio of the vinyl compound (b1): the vinyl compound (c1) of 99:1 to1:99, and thereafter converting said groups of --SO₃ R, --COOR₄ and--OPO(OR₅).sub. 2 to --SO₃ H, --COOH and OPO(OH)₂, respectively.
 11. Adental adhesive composition consisting essentially of the emulsion of awater insoluble polymer consisting essentially of a polymer obtained byemulsion-polymerizing (meth)acrylate in the presence of the emulsion ofa water insoluable polymer as an emulsifying agent, said polymer of thelatter emulsion as the emulsifying agent consisting essentially of apolymer obtained by emulsion-polymerizing (a) a (meth)acrylate and (b1)a vinyl compound having a group of --SO₃ R in which R is hydrogen atomin the absence of a soap in an (a):(b1) molar ratio of 99:1 to 50:50.12. A dental adhesive composition consisting essentially of the emulsionof emulsion of a water insoluble polymer consisting essentially of apolymer obtained by emulsion-polymerizing (meth) acrylate in thepresence of the emulsion of a water insoluble polymer as an emulsifyingagent, said polymer of the latter emulsion as the emulsifying agentconsisting essentially of a polymer obtained by emulsion-polymerizing(a) a (meth) acrylate and (b1) a vinyl compound having a group of --SO₃R in which R is an alkali metal atom or ammonium ion in the absence of asoap in an (a):(b1) molar ratio of 99:1 to 50:50, and thereafterconverting said group of --SO₃ R to --SO₃ H group.
 13. A dental adhesivecomposition consisting essentially of the emulsion of a water insolublepolymer consisting essentially of a polymer obtained byemulsion-polymerizing (meth)acrylate in the presence of a waterinsoluble polymer as an emulsifying agent, said polymer of the latteremulsion as the emulsifying agent consisting essentially of a polymerobtained by emulsion-polymerizing (a) a (meth) acrylate and (b1) a vinylcompound having a group of --SO₃ R in which R is a hydrogen atom and(c1) a vinyl compound containing a group of --COOR₄ in which R₄ is ahydrogen atom or a group of --OPO(OR₅)₂ in which R₅ is a hydrogen atom,in the absence of a soap in the molar ratio of (meth) acrylate (a):total of the two vinyl compounds (b1) and (c1) of 99:1 to 50:50 and themolar ratio of the vinyl compound (b1):the vinyl compound (c1) of 99:1to 1:99.
 14. A dental adhesive composition consisting essentially of theemulsion of a water insoluble polymer consisting essentially of apolymer obtained by emulsion-polymerizing (meth)acrylate in the presenceof the emulsion of a water insoluble polymer as an emulsifying agent,said polymer of the latter emulsion as the emulsifying agent consistingessentially of a polymer obtained by emulsion-polymerizing (a) a(meth)acrylate, (b1) a vinyl compound having a group of --SO₃ R in whichR is an alkali metal atom or ammonium ion and (c1) a vinyl compoundcontaining a group of --COOR₄ in which R4 is an alkali metal atom orammonium ion, or a group of --OPO(OR₅)₂ in which R₅ is an alkali metalatom or ammonium ion, in the absence of a soap in the molar ratio of(meth) acrylate (a):total of the two vinyl compounds (b1) and (c1) of99:1 to 50:50 an in the molar ratio of the vinyl compound (b1): thevinyl compound (c1) of 99:1 to 1:99, and thereafter converting saidgroups of --SO₃ R, --COOR₄ and --OPO(OR₅)₂ to --SO₃ H, --COOH andOPO(OH)₂, respectively.
 15. A dental adhesive primer compositionconsisting essentially of the emulsion of a water insoluble polymerconsisting essentially of a polymer obtained by emulsion-polymerizing(meth)acrylate in the presence of the emulsion of a water insoluablepolymer as an emulsifying agent, said polymer of the latter emulsion asthe emulsifying agent consisting essentially of a polymer obtained byemulsion-polymerizing (a) a (meth) acrylate and (b1) a vinyl compoundhaving a group of --SO₃ R in which R is hydrogen atom in the absence ofa soap in an (a):(b1) molar ratio of 99:1 to 50:50.
 16. A dentaladhesive primer composition consisting essentially of the emulsion of awater insoluble polymer consisting essentially of a polymer obtained byemulsion-polymerizing (meth) acrylate in the presence of the emulsion ofa water insoluble polymer as an emulsifying agent, said polymer of thelatter emulsion as the emulsifying agent consisting essentially of apolymer obtained by emulsion-polymerizing (a) a (meth) acrylate and (b1)a vinyl compound having a group of --SO₃ R in which R is an alkali metalatom or ammonium ion in the absence of a soap in an (a):(b1) molar ratioof 99:1 to 50:50, and thereafter converting said group of --SO₃ R to--SO₃ H group.
 17. A dental adhesive primer composition consistingessentially of the emulsion of a water insoluble polymer consistingessentially of a polymer obtained by emulsion-polymerizing(meth)acrylate in the presence of a water insoluble polymer as anemulsifying agent, said polymer of the latter emulsion as theemulsifying agent consisting essentially of a polymer obtained byemulsion-polymerizing (a) a (meth) acrylate and (b1) a vinyl compoundhaving a group of --SO₃ R in which R is a hydrogen atom and (c1) a vinylcompound containing a group of --COOR₄ in which R₄ is a hydrogen atom ora group of --OPO(OR₅)₂ in which R₅ is a hydrogen atom, in the absence ofa soap in the molar ratio of (meth)acrylate (a) total of the two vinylcompounds (b1) and (c1) of 99:1 to 50:50 and the molar ratio of thevinyl compound (b1):the vinyl compound (c1) of 99:1 to 1:99.